1. Field of the Invention
This invention is in the field of semiconductor devices and is particularly directed to four or more region solid state switching devices.
2. Description of Prior Art
In prior art thyristor or four or more zone solid state switches one or two approaches have been taken to electrically shunt an emitter electrode zone to an adjacent base zone.
Such shunt between the emitter zone and the base zone prevents the unintentional firing of the thyristor without a control current especially at temperatures above the room temperature. In one of the known prior art approaches the shunt is formed so that the emitter electrode extends over the emitter zone and is thereby electrically connected with the adjacent base zone. This is sometimes called the circumferential shunt.
In the case of other thyristors there are provided, either in place of, or in addition to the shunt formed by extending the emitter electrode on to the base zone, several shunts in the form of apertures in the emitter zone through which the base zone extends and is thereby electrically connected with the emitter zone. This is sometimes called hole shunts.
The circumferential shunt is not as effective in case of large-surface thyristors as the hole shunt. The holes located in the emitter zone however hamper the spreading of the turn-on process. But unrestricted spreading of the turn-on process is important especially in case of fast acting thyristors.